To investigate the water conservation function of litter and soil in degraded poplar plantation in Bashang plateau, a sample plot survey was conducted in poplar plantation with three degradations (light degradation, medium degradation and heavy degradation) in Zhangbei from July to September, 2016, and water conservation characteristics of litter and soil were quantitatively analyzed. The results showed that:(1) Litter storage was sorted as light degradation (24.68 t/hm²) > medium degradation (13.43 t/hm²) > heavy degradation (3.66 t/hm²), and the effective retention capacity listed in the order of light degradation (29.28 t/hm²) > medium degradation (23.18 t/hm²) > heavy degradation (3.30 t/hm²), the maximum water-holding capacity followed the order of light degradation (34.90 t/hm²) > medium degradation (24.13 t/hm²) > heavy degradation (3.86 t/hm²), the maximum water-holding rate followed the order of light degradation (228.80%) > medium degradation (228.70%) > heavy degradation (119.94%). There was an logarithmic function relationship between water-holding capacity and immersion time, while a exponential function relationship was found between water-holding rate and immersion time. (2) The soil bulk density of the three poplar plantations ranged from 1.65 to 1.80 g/cm³, capillary porosity ranged from 27.42% to 33.64%, and the range of total porosity ranged was 29.97%~38.57%. (3) There was a power function relationship between soil infiltration rate and infiltration time. The stable infiltration rate followed the order of medium degradation (3.32 mm/min) > light degradation (2.58 mm/min) > high degradation (2.44 mm/min). The water conservation capacity of soil and litter of degraded poplar plantations in Bashang Plateau was at a poor level and decreased significantly with the increasing of degradation degree. Therefore, reasonable tree species selection should be paid attention to during forest managemen, and the seriously degraded forest land should be restored by replanting other tree species or promoting regeneration. The results could provide some theoretical basis and reference for the degradation evaluation and the restoration and reconstruction of local poplar plantation.